1. Field of the Invention
This invention relates to the freeing of stuck or jammed tubulars or other objects downhole and more particularly, to a downhole coiled tubing recovery apparatus and method designed to utilize a resonant frequency oscillator in combination with a specially designed coiled tubing bail for directing coiled tubing directly from a tubing reel through an injector head and to and from the well responsive to raising and lowering of the oscillator and the tubing bail. Freeing of the tubulars or objects is accomplished by typically resonance vibration of the bail and coiled tubing by operation of the oscillator.
Oil field tubulars such as well liners, casing, tubing and drill pipe stuck in a well bore due to various downhole conditions have been one of the principal sources of problems for oil operators and have expanded the business activity of fishing service companies in this century. During this period of time, many new and innovative tools and procedures have been developed to improve the success and efficiency of fishing operations. Apparatus such as electric line free point tools, string shot assisted backoff, downhole jarring tools, hydraulic-actuated tools of various types and various other tools and equipment have been developed for the purpose of freeing stuck or jammed tubulars downhole in a well. Although use of this equipment has become more efficient with time, the escalation in cost of drilling and workover operations has resulted in a proliferation of stuck pipe, liners, casing, and the like downhole, frequently leading to well abandonment as the most expedient resolution of the problem.
The use of vibration and resonant vibration in particular, as a means of freeing stuck tubulars from a well bore has the potential to be immediately effective and thus greatly and drastically reduce the cost involved in tubular recovery operations. Resonance occurs in vibration when the frequency of the excitation force is equal to the natural frequency of the system. When this happens, the amplitude (or stroke) of vibration will increase without bound and is governed only by the degree of damping present in the system.
A resonant vibrating system will store a significant quantity of energy, much like a flywheel. The ratio of the energy stored to the energy dissipated per cycle is referred to as the systems xe2x80x9cQxe2x80x9d. A high energy level allows the system to transfer energy to a given load at an increased rate, much like an increase in voltage will allow a flashlight to burn brighter with a given bulb. Only resonant systems will achieve this energy buildup and exhibit the corresponding efficient energy transmission characteristics which assure large energy delivery and corresponding force application to a stuck region of pipe.
At resonant conditions, a string of pipe will transmit power over its length to a load at the opposite end with the only loss being that necessary to overcome resistance in the form of damping or friction. In effect, power is transmitted in the same manner as the drilling process transmits rotary power to a bit, the difference being that the motion is axial translation instead of rotation. The load accepts the transmitted power as a large force acting through a small distance. Resonant vibration of pipe can deliver substantially higher sustained energy levels to a stuck tubular than any conventional method, including jarring. This achievement is due to the elimination of the need to accelerate or physically move the mass of the pipe string. Under resonant conditions, the power is applied to a vibrating string of pipe in phase with the natural movement of the pipe string.
When an elastic body is subjected to axial strain, as in the stretching of a length of pipe, the diameter of the body will contract. Similarly, when the length of pipe is compressed, its diameter will expand. Since a length of pipe undergoing vibration experiences alternate tensile and compressive forces as waves along the longitudinal axis (and therefore longitudinal strains), the pipe diameter will expand and contract in unison with the applied tensile and compressive waves. This means that for alternate moments during a vibration cycle the pipe may actually be physically free of its bond.
The term xe2x80x9cfluidizationxe2x80x9d is used to describe the action of granular particles when excited by a vibrational source of proper frequency. Under this condition, granular material is transformed into a fluidic state that offers little resistance to movement of body through the media. In effect, it takes some of the characteristics and properties of a liquid. Accordingly, skin friction, that force that confines a stuck tubular, is reduced to a fraction of its normal value due to the effect of vibration because of alternate tensile and compressive forces applied to a pipe and to the fluidization of granular particles packed around the pipe.
Another factor in reducing stuck tubulars downhole is acceleration, wherein a suitable vibrational stroke may need to be only about an inch in order to produce good acceleration for friction reduction and fluidization. Accordingly, the vibrational energy received at the stuck area works to effect the release of a stuck member through the application of large percussive forces, fluidization of granular material, dilation and contraction of the pipe body and a reduction of well bore friction or hole drag.
2. Description of the Prior Art
Resonant vibration systems for use in oilfield tubular extraction applications consist of three basic components: a mechanical oscillator with a suspension device for isolating the rig or support structure, a work string for transmitting vibrational energy, and the stuck tubular or fish to be recovered. The oscillator generates an axial sinusoidal force that can be tuned to a given frequency within a specified operating range. The force generated by the oscillator acts on the work string to create axial vibration of the string. When tuned to a resonant frequency of the system, energy developed at the oscillator is efficiently transmitted to the stuck member with the only losses being those attributed to frictional resistance. The effect of the system reactance is completely eliminated because mass inductance is equal to spring capacitance at the resonant frequency. The total resonant system must be designed so that the components act in concert with one another, thus providing an efficient and effective extraction system.
In conventional coiled tubing operations one of the actions that is detrimental to the life of the coiled tubing is that of continually working the pipe to and from the tubing reel, back and forth over the well entry gooseneck. This action induces bending yield stress into the tubing, which results in accumulated fatigue damage and can eventually lead to fatigue failure of the tubing wall. Modern instrumentation allows monitoring of the tubing bending action and the coil service company will monitor and record that action so that the coil is not used beyond its useful life.
The principal of resonant axial vibration of pipe can be applied to coiled tubing without using the gooseneck equipment. Additionally, it has been found that the coiled tubing does not necessarily need to be cut when used with the downhole coiled tubing recovery apparatus of this invention, thus saving the cost of a reel of tubing, as well as maintaining and enabling good well control, along with the facility for circulating fluids into and from the well.
Various pipe recovery techniques are well known in the art. An early pipe recovery device is detailed in U.S. Pat. No. 2,340,959, dated Feb. 8, 1944, to P. E. Harth. The Harth device is characterized by a suitable electrical or mechanical vibrator which is inserted into the pipe to be removed, such that the vibrator may be activated to loosen the pipe downhole in the well and enable removal of the pipe. A well pipe vibrating apparatus is detailed in U.S. Pat. No. 2,641,927, dated Jun. 16, 1953, to D. B. Grabel, et al. The device includes a vibrating element and a motor-powered drive which is inserted in a well pipe to be loosened and removed, to effect vibration of the pipe and subsequent extraction of the pipe from the well. U.S. Pat. No. 2,730,176, dated Jan. 10, 1956, to W. K. J. Herbold, details a means for loosening pipes in underground borings. The apparatus includes a device arranged within a paramagnetic cylindrical body including a drill, a rod rotatably mounted within the body and a disc member secured to one end of the drill rod, the disc member having a mass which is substantially equally distributed around the axis of the drill rod to define a surface of revolution. A motor is provided for rotating the drill rod and a magnetic apparatus for forcing the disc member into physical contact with the inner walls of the body and into rolling contact with the inner surface of the pipe upon rotation of the drill rod, to loosen the pipe downhole. U.S. Pat. No. 2,972,380, dated Feb. 21, 1961, to A. G. Bodine, Jr., details an acoustic method and apparatus for moving objects held tightly within a surrounding medium. The device includes a vibratory output member of an acoustic wave generator attached to an acoustically-free portion of the stuck tubular. The method includes operating the generator at a resonant frequency to establish a velocity node adjacent to the stuck point and a velocity antinode at the coupling point adjacent to the generator, to loosen the stuck member from the well. U.S. Pat. No. 3,189,106, dated Jun. 15, 1965, to A. G. Bodine, Jr., details a sonic pile driver which utilizes a mechanical oscillator and a pile coupling device for coupling the oscillator body to a pile and applying vibrations of the pile to drive the pile into the ground. U.S. Pat. No. 3,500,908, dated Mar. 17, 1970, to D. S. Barler, details apparatus and method for freeing well pipe. The device includes a number of rotatable, power-driven eccentrics which are connected to an elongated member such as a drill pipe that is stuck in an oil well bore hole and to a resiliently-movable support suspended from the traveling block of an oil derrick. When the power-driven eccentrics are operated, the elongated member is subjected to vertically-directed forces that free it from the stuck position. U.S. Pat. No. 4,429,743, dated Feb. 7, 1984, to Albert G. Bodine, details a well servicing system employing sonic energy transmitted down the pipe string. The sonic energy is generated by an orbiting mass oscillator coupled to a central stem, to which the piston of a cylinder-piston assembly is connected. The cylinder is suspended from a suitable suspension means such as a derrick, with the pipe string being suspended from the piston in an in-line relationship. The fluid in the cylinder affords compliant loading for the piston, while the fluid provides sufficiently high pressure to handle the load of the pipe string and any pulling force thereon. The sonic energy is coupled to the pipe string in the longitudinal vibration mode, which tends to maintain this energy along the string. U.S. Pat. No. 4,574,888 dated Mar. 11, 1986, to Wayne E. Vogen, details a xe2x80x9cMethod and Apparatus For Removing Stuck Portions of A Drill Stringxe2x80x9d. The lower end of an elastic steel column is attached to the upper end of the stuck element and the upper end of the column extends above the top of the well and is attached to a reaction mass lying vertically above, through an accelerometer and vertically-mounted compression springs in parallel with a vertically-mounted servo-controlled, hydraulic cylinder-piston assembly. Vertical vibration is applied to the upper end of the column to remove the stuck element from the well. A xe2x80x9cDevice For Facilitating the Release of Stuck Drill Collarsxe2x80x9d is detailed in U.S. Pat. No. 4,576,229, dated Mar. 18, 1986, to Robert L. Brown. The device includes a first member mounted with the drill pipe disposed in a first position and a second member concentrically mounted with a drill collar or drill pipes in a second position below the first position. Rotation of the drill string from the surface causes a camming action and vibration in a specified operative position of the device, which helps to free stuck portions of the drill pipe. U.S. Pat. No. 4,788,467, dated Nov. 29, 1988, to E. D. Plambeck details a downhole oil well vibrating apparatus that uses a transducer assembly spring chamber piston and spring to effect vibration of downhole tubulers. U.S. Pat. No. 5,234,056, dated Aug. 10, 1993, to Albert G. Bodine, details a xe2x80x9cSonic Method and Apparatus For Freeing A Stuck Drill Stringxe2x80x9d. The device includes a mechanical oscillator employing unbalanced rotors coupled to the top end of a drill string stuck in a bore hole. Operation of the unbalanced rotors at a selected frequency provides resonant vibration of the drill string to effect a reflected wave at the stuck point, resulting in an increased cyclic force at this point.
The prior art is well established regarding the application of vibration to stuck downhole tubulars of the conventional type (threaded pipe). There is no suggestion, however, of any means or method for handling continuous pipe such as coiled tubing, in a vibrational or any other application. It is thus an object of this invention to provide an apparatus and method for working coiled tubing in a stuck pipe or other downhole stuck equipment situation, wherein the coil may be raised and lowered in the well bore by a support structure that includes a lifting and lowering apparatus. Such movement of the coil is accomplished with substantially no bending of the coil string.
Another object of this invention to provide a new and improved downhole coiled tubing recovery apparatus and method for releasing and recovering coiled tubing and other objects stuck or jammed downhole in a well.
Yet another object of this invention is to provide a new and improved downhole coiled tubing recovery apparatus and method which operates utilizing resonant vibration in combination with a specially designed coiled tubing bail to facilitate the release of stuck or jammed coiled tubing from a well.
Another object of the invention is to provide a new and improved coiled tubing recovery apparatus that may be applied to a continuous length of coiled tubing without cutting the tubing, and operated to vibrate the coiled tubing and remove the coiled tubing and other objects from a stuck or jammed position in the well.
A still further object of this invention is to provide a new and improved downhole coiled tubing recovery apparatus which is characterized by specially designed coiled tubing bail adapted to receive a length of coiled tubing from a reel and direct the coiled tubing through an injector head into and from the well, the coiled tubing bail being attached directly to the rig or to an oscillator suspended from the rig for selectively vibrating the coiled tubing and removing the coiled tubing from a stuck or jammed condition in the well.
Still another object of this invention is to provide a downhole coiled tubing recovery apparatus which utilizes an oscillator for attachment to a length of coiled tubing and applying a resonant vibration directly to the coiled tubing for removing the coiled tubing from a stuck or jammed condition in a well.
Another object of this invention is to provide a downhole coiled tubing recovery apparatus and method, which apparatus is characterized by an oscillator suspended from a rig or other support structure and a coiled tubing bail attached to the oscillator for receiving a length of coiled tubing extending from a coiled tubing reel and directing the coiled tubing through an injector head into the well, such that the oscillator can be operated to vibrate the coiled tubing, typically at a resonant frequency, and remove the coiled tubing from a stuck or jammed condition in the well.
Yet another object of the invention is to provide a coiled tubing recovery apparatus and method which is designed to vibrate jammed or stuck coiled tubing and reduce the friction of tubing insertion and extraction in a well.
These and other objects of the invention are provided in new and improved coiled tubing recovery apparatus and method, which apparatus is characterized in a preferred embodiment by a specially designed coiled tubing bail suspended directly from a rig structure or from an oscillator that is further suspended from the travelling block or other supporting structural element of an oil derrick or rig. The method of this invention includes directing the coiled tubing from a reel through a set of rod clamps in the coiled tubing bail and through an injector head, into the well bore. In the event of a stuck or jammed condition of the coiled tubing in the well bore, the coiled tubing bail can be lifted and/or the oscillator can be lifted and operated to apply resonant vibration through the coiled tubing bail and the coiled tubing to loosen the coiled tubing in the well hole.